High-temperature components, e.g. turbine blades or vanes, are actively cooled and therefore have cylindrical and/or shaped cooling-air holes with a diffuser at the surface.
When reusing the turbine blades or vanes, wherein a coating is removed from the turbine blades or vanes and a new coating is applied, the cooling-air holes which are already present may in some cases become blocked. The coating in the holes and in the diffuser (coat down) has to be removed, which is often carried out by means of a special EDM electrode.